Agitating and aerating means for flotation cells



Patented Feb. 24, 1942 UNITED STATES PATENT OFFICE AGITATING ANDAERATING MEAN FOR FLOTATION CELLS Frank A. Dromgold, Brisbane, Calif.Application August 5, 1940, Serial No. 351,455 6 Claims. (01. 261 93) Mypresent invention relates to improvements in flotation apparatus andmore particularly to a new and improved cell in which a pulp agitatingand aerating means is journalled in the bottom of the cell and driven bymeans located below the cell. i

and improved rotary agitating and aerating device for flotationapparatus which may be journalled in the bottom of any suitable pulpcontaining cell and driven from a source of power located therebelow ina convenient and ,eificient manner.

Another object of my invention is to provide a new and improved rotaryagitating and aerating device for flotation cells and a mountingtherefor by means of which airand/or a re-agent may be introducedthrough the bottom of the flotation cell.

Another object of the invention is to provide an improved rotaryagitating and aerating device that is journalled upon bearings mountedin the bottom of a flotation cell and which has novel means to'protectthe bearings and prevent the escape of pulp from the cell at this point.

In the operation of ore separating flotation cells employing rotaryagitating and aerating members it has always been a problem to provide asuitablejournal support for the rotary agi tating and aerating member.This is due to the fact that the rotary agitating and aerating member issubmerged below the surface of the pulp where, because of leakage andthe abrasive action of the solid particles of the pulp, it has beenfound difficult to provide a suitable bearing support for the rotaryagitating and aerating 'memher. To remedy this situation it hasgenerally been the practice to mount the rotary agitating and aerating.member upon the lower end of a shaft which is suspended from bearingslocated above and in an overhanging position with respect to the cell.While this arrangement provides a bearing support for the rotaryagitating and aerating member which i free from attack by the abrasiveaction of the pulp and avoids an opening in the bottom of the cell, ithas the disadvantage that the overhanging supporting structure for thebearings renders the cells more or less inaccessible at the top thereofand is subject to the possibility of oil dripping into the pulp fromthese bearings. A more serious objection,

however, is that with this type of mounting it is difficult to maintainthe fine balance in the rotary agitating and aerating member which isnecessary in order to prevent excessive vibration 56 An object of myinvention is to provide a new when the apparatus is in operation. It is,therefore, a further object of my invention to provide a rotaryagitating and aerating device which may be mounted upon a relativelyshort shaft that is journalled in a bearing secured in the bottom of thecell and which is adapted to be driven by power means located below thecell.

Other objects and advantages of the invention I will be in part evidentto those skilled in the art and in part pointed out hereinafter as thedescription thereof taken in connection with the v accompanying drawingproceeds.

In the accompanying drawing wherein there is shown by way ofillustration and not of limitation n Figure 1 is a vertical sectionalview taken centrally through a series of flotation cells and havingagitating and aerating means constructed in accordance with the presentinvention;

Figure 2 is a fragmentary plan view showing a portion of the cellarrangement illustrated in Figure 1 of the drawing;

Figure 3 is a vertical sectional view taken along line 3-3 of Figure 2looking in direction of the arrows, and

Figure 4 is an enlarged sectional view taken centrally through apreferred form of my improved agitating and aerating device and themounting therefor.

In the separation of mineral values from ore by means of the flotationprocess it is important that a sufficient amount of air be introducedinto the pulp during agitation to thoroughly aerate the pulpand producea maximum amount of 7 substantially uniformly throughout the pulp.

The'present invention is considered to be an improvement upon thearrangementdescribed and claimed in my copending application SerialNumber 254,493 filed February 3, 1939, and entitled Material separationdevices in that the present construction and arrangement of theagitating element and impeller blades more vveffectively cooperate todistribute the aerating air and includes additional means by which amore effective sealing of the flotation cell about the agitatorsupporting bearing is eifected.

Reference is now made to the drawing for a more detailed description ofmy invention. As is well understood flotation ore concentratingapparatus of the type contemplated generally consists of a series ofcells through which the ore containing pulp is successively circulatedand subjected to removal of the mineral values by the discharge of afoam or froth at the side of each of the cells. In Figure 1, there isshown the first two cells of a series designated by the numerals Hi andH and a portion of a third cell 12, which it is to be understood will bethe end cell of a series of similar cells. The cell it, which is thefirst of the series has a feed hopper l3 through"which the orecontaining pulp is originally introduced into the flotation apparatuswhere it will be subjected to agitation and aeration, as willhereinafter appear, by means of a combined agitating and aerating devicedesignated generally by the numeral Q-' As the pulp is thus subjected toagitation and aeration in the presence of a suitable re-agent, themineral values will be taken up by the bubbles formed due to thisagitation and aeration and will rise through a horizontal baiile l5which will tend to cause the mineral value carrying foam to risesubstantially vertically. At the same time the tailihgs accumulating inthe cell it will pass through a communicating passageway iii formed in awall i'l between the cells iii and H and the note or foam in the cell'sill and M will obtain a corresponding level due to a second passage-,way l8 which is formed above the baffles H5 in the wall l'l between thecells Ill and ii. I Similarly the taili'n'gs accumulating in and thefroth produced in cell ll will flow on to the succeeding cells of theseries through openings [9 and 29 formed in walls 2| between the nextandfollowing cells. As the tailings and the value bearing foam producedin each of the cell's circulates through the apparatus to the succeedingcells, the uppermost portions of the value bearing foam will be spilledover the sides of the cells and collected in a launder where they maybesubjected to further recovery processes. After the pulp has thuscirculated through the series of cells Ni, ii, etc., it will finallycollect in the last cell i2 of the series where the tailings will bedischarged through an outlet 22 formed in an end 'wallZS and into achamber 2% from which it will be nnany discharged through a conduit 25.As here shown, the chamber 2d has anwadj-ustable weir gate 2'6 which maybe raised and lowered to "maintain any desired level of pulp throughoutthe series of cells.

Before passing on to the remaining figures of the drawing, it should benoted that the agitating and aerating devices M are shown as carried bysuitable supporting bearings 2-1 that are secured in openings formedcentrally in the bottoms of the cells H), H and I2. These agitating andaerating devices M are carried by hollow shafts 28 that are journaied inthe supports 2-1. The shafts 28 also carry suitable pulleys 29 at theirlower ends, about which driving belts 30 Two of the driving belts 363are here shown of "the cells 1-6 and H to a double pulley-3i that isdriven by a vertically disposed electric motor '32. In practice it iscontemplated that a single motor 32 maybe utilized to drive a pluralityof agitating and aerating devices hi and in this manner the number ofmotors required may be reduced to a minimum as the character of theagitating and aerating devices i l and their journaled supports willrequire a relatively small amount of power to maintain successfuloperation thereof. The agitating and aerating devices i l, three ofwhich are shown in Figure 1 of the drawing, are of substantiallyidentical construction, except for certain details that have to do withthe manner in which the flow of air and/ or a re-agent to the agitatingand aerating devices H3 is controlled. The agitating device l4, shown asdisposed in the cell lfiL-is of a construction corresponding to thatillustrated in detail in Figure 4 of the drawing. It has a ball checkvalve at the upper end of the hollow shaft 28, as is shown at the upperend of the assembly illustrated in Figure 4 of the drawing. Theagitating device it located in the cell H is similar to the assemblyillustrated in detail in Figure 4 of the drawing, except that no checkvalves are provided in the hollow shaft 28. In this arrangement thehollow shaft 28 which supports the agitating device H3 is provided witha pipe-like extension 33 that extends upwardly above the level of thepulp in the cell I l and at its lower end the hollow shaft '28 isprovided with a suitable plug '34. When the hollow shaft 28 is equippedin this manner, it will be understood that the aerating air will bedrawn downwardly through the pipe-like extension 33 and discharged intothe pulp by the agitating and aerating device M. The agitating device itshown as disposed in the cell i2 is identical with the agitating devicel4 shown in cell It), except that the check valve shown in full lines inFigure 4 of the drawing is positioned at the lower end of the hollowshaft 28, as shown by dot and dash lines in this latter figure of thedrawing.

Upon referring to Figures 2 and 3 of the drawing, it will be seen thatthe horizontal baiiles l5 extend across the entire area of each of thecells and provide a series of rectangular passageways through which theagitated pulp will rise in a substantially vertical direction. In otherwords, the ba'iiies '55 will serve to limit a swirling of the pulp bythe agitators M to the area therebelow and thus permit the froth or foamto rise in the cells when the mineral values have been collectedthereby. As the froth or foam with the mineral values continues to risethrough the baiiles i5, it will spillover the sides of each of the cellsand be collected by a launder to be subjected to further recoveryprocesses. As shown, particularly in Figure 3 of the drawing, acorresponding side of each of the cells it, ll, etc. is provided with anoutwardly inclined wall it in which there is provided a weir comprisedof a series of superimposed slats that may be positioned therein todetermine the level of the froth in the particular cell. Associated withthis weir 35 there is also a longitudinally extending shaft 31 thatcarries a rotatable paddle -38 which, when rotated in the direction oiarrows as here s-hown, will serve to propel the froth with its mineralvalues over the weir 3%. As an additional improvement, each of the cellsill, H, 1'2, etc. is here shown as provided with an inwardly disposed'bafiie 39 which tends -to direct the new of froth toward the weir 36and -a second inwardly disposed baiiie 40 which directs the flow offroth or foam at this point toward'the ba-file 39of each'of the-cells.Asmall by-pass port 41 is show-n at the bottom of the baffle 30 throughwhich unspilled-pdlp may return to the agitating zone-of thecells.

form'a pedestal-like support for an upper bearing 43. "At its lower endthe cylindrical housing 42 carries a similarbearing 44., These bearings43 21 andbelow the bearing 44 there is provided a packing gland 45whichcarries a suitable sealing ring- 48 and a porous packing 41, andscrewed into the upper endof the tubular portion 42 of the supp rt2l'there is a packing gland 48 that carries two opposed sealing rings 49and a porous packing ring'5fl, When the packing glands 45 and 48 arescrewed into the tubular. portion 42 of the support 21', they willnormally serve to retain lubricating grease which is supplied through agrease connection in the bearings 43 and 44. In order to provide againstthe escape of liquidpulp alongthe hollow shaft 28, the present inventionalso contemplates the provsionof a conduit 52 in the tubular portion 42through which air, gas or other fluid from a source 53 may flow to theporous packing ring 50 and out through the end of the packing gland 48.Cooperating with this flow of air, gas or other fluid under pressurethrough the conduit 52 and the packing gland 48, the agitating andaerating device I 4 carries a depending flange or skirt 54 thattelescopes downwardly over the upwardly extending end of the support 2'!so as to provide what maybe termed an inverted bell into which air mayaccumulate and prevent the entrance of pulp upwardly into this space.With this construction, it will be seen that when air, gas or otherfluid flows through the conduit 52 from the source 53, a pressure willbe created in the inverted bell thus formed and as a result the shaft,sealing rings and packings, and also the bearings of the shaft 28 willbe protected against the abrasive action of the pulp under treatment inthe cell. v

While the shape and the construction of the agitating and aeratingmembers I 4 may take many forms, it will be found that when thesedevices are, provided with a frusto-conical top or web forming portion55 and a plurality of downwardly extending blades 56 arranged radiallywith, respect to the axis of the hollow shaft 28, the agitation set upthereby will be most effective as the air and general motion of the pulpwill be outwardly and downwardly at the center of the cells. As hereshown, the upper end of the hollow shaft 28 is closed by a plug 5'! andcarries a ball check valve 58 which cooperates with a rubber seat 59 toprevent the passage of liquid pulp downwardly through the hollowshaft28. At the same time, when the agitating and aerating device I4 is inrotation, the blades 58 carried. thereby will throw the liquid outwardlyand thus create a suction which will lift the ball valve 58 from itsseat 59 and permit a flow of air and/or a re-agent through ports 68 andinto the space beneath the frusto-conical web forming portion 55 whereit will be discharged outwardly and into the pulp to aerate same. Toilustrate a modified arrangement in which a check valve is provided atthe lower end of the hollowshaft .28, there is shown in this figure ofthe drawing at the lower end of the hollow shaft 28, by dot and upwardlythrough the bottom of the cell ID to dash lines, a connnecting collar 6|;thatfcarries a check valve cage 62 and a ball valve 63 which may besubstituted for the check valve 58 or which may be used simultaneouslytherewith.

With the above described arrangement it will be readily seen that whenthe flotation apparatus is in operation and pulp is introduced into celll0 through the feed hopper l3, the pulp will flow through the successivecells and be agi-' tated by the respective agitating and aeratingmeansl4. At the same time the froth or foam carrying the mineral valueswill be carried upwardly through the baffles I 5 and discharged over theWeirs 36 provided upon the several cells and finally collected in thelaunder for further recovery treatment. Due to the agitating and airpropelling action of the blades 56 upon the agitating device [4, it willalso be understod that air and/or a re-agent will be drawn into each ofthe cells through the hollow shafts 28 associated with their respectiveagitating and aerating devices 14. Additional air may also be injectedinto the pulp from the source 53 through the conduit 52. If the source53 is adapted to supply an oil or oily re-agent, this fluid may besubstituted for air and in this event it will be seen that such ,oilwill, in addition to preventing the escape of pulp from the cell, alsosupplement the normal lubricating function of the grease which isnormally supplied to the bearings 43 and 44 through the grease coupling5|. In the event that the apparatus is required to be shut down withoutdraining the cells, it will also be seen that the check valve 58 and/orthe check valve 63 will become operative immediately upon a stopping ofthe agitating and aerating device I4 and prevent the escape of pulp fromthe cells through the hollow shafts 28.

While I have, for the sake of clearness and in order to disclose myinvention so that the. same i can be readily understood, described andillustrated specific devices and arrangements, I desire to have itunderstood that this invention is not limited to the specific meansdisclosed, but may be embodied in other ways that will suggestthemselves to persons skilled in the art. For example, where the termair is used in the claims, it is to be understodthat gas and otherfluids may be substituted therefor. It is believed that this inventionis new and it is desired to claim it so that all such changes as comewithin the scope of the appended claims are to be considered as part ofthis invention. Having thus described my invention, what I claim anddesire to secure by Letters Patent is- 1. In flotation apparatus of thecharacter described, the combination of a pulp receiving receptacle, abearing pedestal secured to and extended through the bottom of saidreceptacle, a shaft journalled in and projected upwardly through saidpedestal to rotate about a vertical axis, a pulp agitating and aeratingmeans secured to the upper end-.o-f said shaft and disposed below thesurface of the pulp within said pulp receiving receptacle, saidagitating and aerating means having a hub with a circular web formingportion and radially extending impeller blades depending therefrom whichproduce a downward circulation of entrained air, and a downwardlyextending cylindrical flange carried by said hub adapted to telescopeover said pedestal downwardly extending cylindrical flange thattelescopes over said bearing pedestal and provides an inverted airretaining bell into which the upper end of said bearing supportingpedestal extends, and means for introducing air under pressure into saidinverted air retaining bell to thus form an air seal which will preventthe pulp in said receptacle from coming into contact with said shaft orescaping through said anti-friction ball bearing means.

3. In an agitating and aerating means for flotation ore concentratingapparatus, the combination of an orc pulp containing receptacle, a

vertically disposed shaft supporting pedestal secured to and extendingupwardly from the bottom of said ore pulp containing receptacle, ahollow shaft journalled in said pedestal and communicating with theatmosphere adapted to rotate about a vertical axis, a pulp agitatingmember secured to the upper end of said shaft having a frusto-conicaltop portion and ports located beneath said frusto-conical top portioncommunicating with the interior of said hollow shaft, a series ofradially extending agitator blades depending from said frusto-conicalportion, means for driving said hollowvertical shaft, whereby air willbe drawn. through said hollow shaft to said ports and dischargeddownwardly by said blades into the pulp as said agitating member isrotated by said shaft driving means, and means carried by said pulpagitating member forming an inverted bell over said shaft supportedpedestal, said inverted bell being adapted to entrap a portion of theair discharged downwardly by said blades and form an air seal about saidhollow shaftwhich will prevent the escape of'pulp from I thepulpcontaining receptacle at this point.

4. In an agitating and aerating means for flotation ore concentratingapparatus, the combination of an ore pulp containing receptacle havingan opening in the bottom thereof, a ver- 1 tically disposed shaftsupporting pedestal secured in said opening and extending upwardly intothe ore pulp containing receptacle,. a hollow shaft journalled in saidpedestal and adapted to rotateabout a vertical axis, said hollow shaftbeing closed at its upper and open to the atmosphere at its lower end, arotary pulp agitating member secured upon said shaft having a.frusto-conical portion and ports located beneath said frustoconicalportion communicating withthe interior of said hollow shaft, a seriesof'radially extending agitator blades depending from said frustoconicalportion, means located below the bottom of said cell for driving saidhollow vertical shaft, whereby air will be drawn through said hollowshaft to said ports and discharged downwardly by said blades into thepulp as said agitating member is rotated by said shaft driving means,and a skirt-like member carried by said agitating member forming aninverted bell over said shaft supported pedestal, said inverted bellbeing adapted to entrap a portion of the air discharged downwardly bysaid blades and form an air seal about said hollow shaft which willprevent the escape of pulp from said receptacle at this point.

5. In an agitating and aerating means for flotation oreconcentratingapparatus, the combination of an ore pulp containing receptacle havingan opening in the bottom thereof, a vertically disposed shaft supportingpedestal in and closing said opening and extending upwardly into theorepulp containing receptacle, a hollow shaft journalled in said pedestaland adapted to rotate about a vertical axis, a rotary pulp agitatingmember secured to the upper end of said shaft having a conical webforming portion with ports located therebelowcommunicating with theinterior of said hollow shaft, a series of radially extending agitatorblades adjacent said port and depending from said conical web formingportion, means for driving said hollow vertical shaft, whereby air willbe drawn through said hollow shaft to said ports and dischargeddownwardly by said blades into the pulp as said agitating member isrotated by said shaft driving means, and a skirt-forming flange belowthe radially extending blades upon said agitating member adapted totelescope over the upwardly extending end of said pedestal and form aninverted bell in which some of the air discharged downwardly by saidblades will be entrapped to provide an air seal and prevent the escapeof pulp along'said shaft and through said bearing pedestal.

6. In flotation apparatus of the character described, the combination ofa pulp receiving receptacle, a bearing pedestal secured to and extendedthrough the bottom of said receptacle, a shaft journaled in andprojected upwardly through said pedestal to rotate about a verticalaxis, a pulp aerating means secured to the upper end of said shaft anddisposed below the surface of pulp within said pulp receivingreceptacle, said pulp aerating means having radially extending impellerblades depending therefrom which produce a downward circulation ofentrained air, a downwardly extending cylindrical flange carried by saidmeans below said blades and adapted to telescope over said pedestal andprovide an inverted bell in which a portion of said entrained air willaccumulate and form an air seal about said shaft which will preventcontact of the pulp with said shaft and the escape of pulp from saidreceptacle through said bearing pedestal, and means including a conduitextending upwardly through said, pedestal for introducing additional airunder pressure into said inverted bell.

FRANK A. DROMGOLD.

